Four Commanderies of Han
The Four Commanderies of Han (Chinese: 漢四郡; pinyin: Hàn-sìjùn; Korean: 한사군; Hanja: 漢四郡; RR: Han-sagun) were Chinese commanderies located in the north of the Korean Peninsula and part of the Liaodong Peninsula from around the end of the second century BCE through the early 4th CE, for the longest lasting. The commanderies were set up to control the populace in the former areas of Old Chosŏn (Gojoseon) as far south as the Han River, with a core area at Lelang near present-day Pyongyang by Emperor Wu of the Han dynasty in early 2nd century BCE after his conquest of Wiman Chosŏn.